Aufgaben:Exercise 3.5: GSM Full Rate Vocoder - Revision history

Guenter at 09:39, 25 January 2023

2023-01-25T09:39:00Z

Guenter at 09:23, 25 January 2023

2023-01-25T09:23:42Z

Guenter: Guenter moved page Aufgaben:Exercise 3.5: GSM Full Rate Codec to Aufgaben:Exercise 3.5: GSM Full Rate Vocoder

2023-01-25T09:02:56Z

Guenter moved page Exercise 3.5: GSM Full Rate Codec to Exercise 3.5: GSM Full Rate Vocoder

Guenter: Guenter moved page Aufgaben:Exercise 3.5: GSM Full-Rate Voice Codec to Aufgaben:Exercise 3.5: GSM Full Rate Codec

2023-01-25T09:01:33Z

Guenter moved page Exercise 3.5: GSM Full-Rate Voice Codec to Exercise 3.5: GSM Full Rate Codec

Hwang at 11:23, 23 January 2023

2023-01-23T11:23:55Z

Hwang at 11:23, 23 January 2023

2023-01-23T11:23:01Z

Noah at 19:37, 21 January 2023

2023-01-21T19:37:45Z

Noah at 19:37, 21 January 2023

2023-01-21T19:37:08Z

Noah at 19:36, 21 January 2023

2023-01-21T19:36:46Z

Show changes

Noah at 19:06, 21 January 2023

2023-01-21T19:06:13Z

@@ Line 78: / Line 78: @@
 {{ML-Kopf}}
-'''(1)'''&nbsp; To satisfy the sampling theorem, the bandwidth must not exceed $f_{\rm A}/2 \hspace{0.15cm} \underline{= 4 \ \rm kHz}$.
+'''(1)'''&nbsp; To satisfy the sampling theorem,&nbsp; the bandwidth must not exceed&nbsp; $f_{\rm A}/2 \hspace{0.15cm} \underline{= 4 \ \rm kHz}$.
-'''(2)'''&nbsp; From the given sampling rate $f_{\rm A} = 8 \ \rm kHz$ results a distance between individual samples of $T_{\rm A} = 0.125 \ \rm ms$.
+'''(2)'''&nbsp; From the given sampling rate&nbsp; $f_{\rm A} = 8 \ \rm kHz$ &nbsp; results a distance between individual samples of&nbsp; $T_{\rm A} = 0.125 \ \rm ms$.
-*Thus, a speech frame $(20 \ \rm ms)$ consists of $N_{\rm R} = 20/0.125\hspace{0.15cm} \underline{= 160 \ \rm samples}$, each quantised with $13 \ \rm bits$.
+*Thus,&nbsp; a speech block $(20 \ \rm ms)$ consists of $N_{\rm block} = 20/0.125\hspace{0.15cm} \underline{= 160 \ \rm samples}$,&nbsp; each quantized with&nbsp; $13 \ \rm bits$.
 *The data rate is thus
-:$$R_{\rm In} = \frac{160 \cdot 13}{20 \,{\rm ms}} \hspace{0.15cm} \underline {= 104\,{\rm kbit/s}}\hspace{0.05cm}.$$
+*The data rate&nbsp; is thus
-'''(3)'''&nbsp; From the graph, it can be seen that $36$ (LPC) $+ 36$ (LTP) $+ 188$ (RPE) $= 260 \ \rm bits$ are output per speech frame.
+'''(3)'''&nbsp; From the graph,&nbsp; it can be seen that&nbsp; $36$&nbsp; (LPC)&nbsp; $+\ 36$&nbsp; (LTP) $+\ 188$&nbsp; (RPE)&nbsp; $= 260 \ \rm bits$&nbsp; are output per speech block.
-*From this, the output data rate is calculated to be
+*From this,&nbsp; the output data rate is calculated to be
-:$$R_{\rm Out} = \frac{260}{20 \,{\rm ms}} \hspace{0.15cm} \underline {= 13\,{\rm kbit/s}}\hspace{0.05cm}.$$
+:$$R_{\rm out} = \frac{260}{20 \,{\rm ms}} \hspace{0.15cm} \underline {= 13\,{\rm kbit/s}}\hspace{0.05cm}.$$
-'''(5)'''&nbsp; Correct are <u>statements 1 and 3</u>, but not the second:
+*The LPC output signal has a significantly smaller amplitude compared to its input&nbsp; $s_{\rm block}(n)$,&nbsp; has a significantly reduced dynamic range and a flatter spectrum.
-'''(6)'''&nbsp; Correct are <u>statements 2 and 3</u>:
+'''(5)'''&nbsp; Correct are the&nbsp;  <u>statements 1 and 3</u>,&nbsp; but not the second:
-*That statement 1 is false can already be seen from the graph on the statements page, since $188$ of the $260$ output bits come from the RPE.
+*The LTP analysis and filtering is done in blocks every $5 \rm ms \ (40 \rm samples)$,&nbsp; i.e.&nbsp; four times per speech block.
-*To the last statement:&nbsp; The RPE searches for the subsequence with the maximum energy.
-*This parameter "RPE pulses" alone occupies $156$ of the $260$ output bits.
+*To do this,&nbsp; the cross-correlation function (CCF) is formed between the current and the three preceding sub-blocks.
 {{ML-Fuß}}

@@ Line 4: / Line 4: @@
 [[File:EN_Mob_A_3_4_Z.png|right|frame|LPC, LTP and RPE parameters in the GSM Full Rate Vocoder]]
-This codec called "GSM Full Rate Vocoder"&nbsp; (which was standardized for the GSM system in 1991)&nbsp;  stands for a joint realization of coder and decoder and combines three methods for the compression of speech signals:
+This codec called&nbsp; "GSM Full Rate Vocoder"&nbsp; (which was standardized for the GSM system in 1991)&nbsp;  stands for a joint realization of encoder and decoder and combines three methods for the compression of speech signals:
 *Linear Predictive Coding&nbsp; $\rm (LPC)$,
-*Long Term Prediction&nbsp; $\rm (LTP)$, and
+*Long Term Prediction&nbsp; $\rm (LTP)$,&nbsp; and
 *Regular Pulse Excitation&nbsp; $\rm (RPE)$.
-The numbers shown in the graphic indicate the number of bits generated by the three units of this Full Rate speech codec per frame of&nbsp; $20$&nbsp; millisecond duration each.
+The numbers shown in the graphic indicate the number of bits generated by the three units of this full rate speech codec per frame of&nbsp; $20$&nbsp; millisecond duration each.
-It should be noted that LTP and RPE, unlike LPC, do not work frame by frame, but with sub-blocks of&nbsp; $5$&nbsp; milliseconds.&nbsp; However, this has no influence on solving the task.
+It should be noted that LTP and RPE,&nbsp; unlike LPC,&nbsp; do not work frame by frame,&nbsp; but with sub-blocks of&nbsp; $5$&nbsp; milliseconds.&nbsp; However,&nbsp; this has no influence on solving the exercise.
-The input signal in the above graphic is the digitalized speech signal&nbsp;  $s_{\rm R}(n)$.
+The input signal in the above graphic is the digitalized speech signal&nbsp;  $s_{\rm block}(n)$.&nbsp; This results from the analog speech signal&nbsp; $s(t)$&nbsp; by
-This results from the analog speech signal&nbsp; $s(t)$&nbsp; by
+*sampling at the sampling rate&nbsp; $f_{\rm A} = 8 \ \rm kHz$,
-*sampling at the sampling rate $f_{\rm A} = 8 \ \rm kHz$,
+*quantization with&nbsp; $13 \ \rm bits$,
 *following segmentation into blocks of each&nbsp;$20 \ \rm ms$.
@@ Line 29: / Line 27: @@
 The further tasks of preprocessing will not be discussed in detail here.
-*This exercise belongs to the chapter&nbsp; [[Examples_of_Communication_Systems/Voice_Coding|"Speech Coding"]].
+<u>Hint:</u> &nbsp; This exercise belongs to the chapter&nbsp; [[Examples_of_Communication_Systems/Voice_Coding|"Speech Coding"]].
@@ Line 49: / Line 43: @@
 $B \ = \ $ { 4 3% } $ \ \rm kHz$
-{How many samples&nbsp; $(N_{\rm R})$&nbsp; does a speech frame consist of? What is the input data rate&nbsp; $R_{\rm In}$?
+{How many samples&nbsp; $(N_{\rm block})$&nbsp; does a speech lock consist of?&nbsp; What is the input data rate&nbsp; $R_{\rm in}$?
 |type="{}"}
-$N_{\rm R} \hspace{0.25cm} = \ $ { 160 3% }
+$N_{\rm block} \hspace{0.25cm} = \ $ { 160 3% }
-$R_{\rm In} \hspace{0.22cm} = \ $ { 104 3% } $\ \rm kbit/s$
+$R_{\rm in} \hspace{0.22cm} = \ $ { 104 3% } $\ \rm kbit/s$
-{What is the output data rate&nbsp; $R_{\rm Out}$&nbsp; of the GSM full rate codec?
+{What is the output data rate&nbsp; $R_{\rm out}$&nbsp; of the GSM full rate codec?
 |type="{}"}
-$R_{\rm Out} \hspace{0.09cm} = \ $ { 13 3% } $ \ \rm kbit/s$
+$R_{\rm out} \hspace{0.09cm} = \ $ { 13 3% } $ \ \rm kbit/s$
-{Which statements are true regarding the block "LPC"?
+{Which statements are true regarding the block&nbsp; "LPC"?
 |type="[]"}
 + LPC makes a short-term prediction over one millisecond.
 + The&nbsp; $36$&nbsp; LPC bits are filter coefficients used at the receiver to undo the LPC filtering.
 - The filter for long-term prediction is recursive.
-- The LPC output is identical to its input&nbsp; $s_{\rm R}(t)$.
+- The LPC output is identical to its input&nbsp; $s_{\rm block}(t)$.
 {Which statements are true regarding the block "LTP"?
 |type="[]"}
 + Periodic structures of the speech signal are removed.
-- Long-term prediction is performed once per frame.
+- Long-term prediction is performed once per block.
 + The memory of the LTP predictor is up to&nbsp; $15 \ \rm ms$.

← Older revision		Revision as of 11:23, 23 January 2023
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−	[[Category:Examples of Communication Systems: Exercises\|^3.3 ~~Voice~~ Coding^]]	+	[[Category:Examples of Communication Systems: Exercises\|^3.3 Speech Coding^]]

@@ Line 3: / Line 3: @@
 }}
-[[File:EN_Mob_A_3_4_Z.png|right|frame|LPC, LTP and RPE parameters in the GSM Full-Rate Vocoder]]
+[[File:EN_Mob_A_3_4_Z.png|right|frame|LPC, LTP and RPE parameters in the GSM Full Rate Vocoder]]
-This codec called "GSM Full-Rate Vocoder"&nbsp; (which was standardized for the GSM system in 1991)&nbsp;  stands for a joint realization of coder and decoder and combines three methods for the compression of speech signals:
+This codec called "GSM Full Rate Vocoder"&nbsp; (which was standardized for the GSM system in 1991)&nbsp;  stands for a joint realization of coder and decoder and combines three methods for the compression of speech signals:
 *Linear Predictive Coding&nbsp; $\rm (LPC)$,
@@ Line 12: / Line 12: @@
-The numbers shown in the graphic indicate the number of bits generated by the three units of this Full-Rate speech codec per frame of&nbsp; $20$&nbsp; millisecond duration each.
+The numbers shown in the graphic indicate the number of bits generated by the three units of this Full Rate speech codec per frame of&nbsp; $20$&nbsp; millisecond duration each.
 It should be noted that LTP and RPE, unlike LPC, do not work frame by frame, but with sub-blocks of&nbsp; $5$&nbsp; milliseconds.&nbsp; However, this has no influence on solving the task.
@@ Line 36: / Line 36: @@
 Hint:
-*This exercise belongs to the chapter&nbsp; [[Examples_of_Communication_Systems/Voice_Coding|"Voice Coding"]].
+*This exercise belongs to the chapter&nbsp; [[Examples_of_Communication_Systems/Voice_Coding|"Speech Coding"]].

← Older revision		Revision as of 19:37, 21 January 2023
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	You can also take questions and solutions (almost completely?) from		You can also take questions and solutions (almost completely?) from
−	[https://en.lntwww.de/Aufgaben:Exercise_3.4Z:_GSM_Full-Rate_Voice_Codec " Exercise 3.4Z"]	+	[https://en.lntwww.de/Aufgaben:Exercise_3.4Z:_GSM_Full-Rate_Voice_Codec " Exercise 3.4Z"].

← Older revision		Revision as of 19:37, 21 January 2023
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	Hint:		Hint:

−	*~~Diese Aufgabe gehört zum Kapitel~~  [[Examples_of_Communication_Systems/Voice_Coding\|"Voice Coding"]].	+	*This exercise belongs to the chapter  [[Examples_of_Communication_Systems/Voice_Coding\|"Voice Coding"]].

← Older revision		Revision as of 19:06, 21 January 2023
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−	{{quiz-Header\|Buchseite=~~Beispiele von Nachrichtensystemen~~/~~Sprachcodierung~~	+	{{quiz-Header\|Buchseite=Examples_of_Communication_Systems/Voice_Coding
	}}		}}